[unreadable] This grant application requests support for the 21st Gordon Research Conference (GRC) on the Chemistry and Biology of Tetrapyrroles at Salve Regina University, Newport, Rl (July 23-28, 2006). Since1966, this biennial interdisciplinary conference has fostered collaborations between basic scientists including biochemists, biologists, chemists and clinicians interested in tetrapyrroles. In a variety of protein environments, tetrapyrroles have diverse roles providing redox catalysts to harvest light energy and to activate, deliver and sense diatomic gases (e.g. oxygen, carbon monoxide and nitric oxide) often acting as signaling systems. Tetrapyrroles are essential nutrients (e.g. vitamin B12); regulate protein expression via transcriptional and translational effects (e.g. heme); and provide novel therapeutic agents for photodynamic cancer therapy and targeted delivery of radionuclides. But due to their photodynamic, toxic and lipophilic properties some tetrapyrroles (e.g. porphyrins, bilirubin) accumulate in cells of the skin, liver and brain, producing diverse pathologies (e.g. porphyrias). Thus, this GRC represents an important venue for exchange between basic and applied researchers on tetrapyrroles and for refinement of new tools and therapies under development by the biomedical industry. Sessions have been specifically devised to showcase the advances made by these investigators including new sessions: tetrapyrrole trafficking (e.g. intracellular transporters); tetrapyrroles in complex biological processes (e.g. circadian rhythms; global iron homeostasis); nanostructures and artificial heme-proteins; and, a workshop on the porphyrias with a focus on metabolomics. This program includes 28 invited speakers, a plenary lecturer, and 9 discussion leaders, selected for their scientific excellence and recent innovative work that makes significant contributions to the breath of the program. The remaining approximately 100 conferees will be chosen to ensure a broad representation of women, ethnicity and young scientists from various disciplines in academia, medical research institutions and industry. The strengths of this established GRC are its disciplinary diversity, focus on new unpublished work, time for discussion, informal atmosphere and ban on dissemination of conference proceedings. [unreadable] [unreadable]